The present invention describes an improved electrostatic sector used in miniaturized mass spectrometry applications.
Much effort has been placed on miniaturization of a high performance mass spectrometer. Such could be used in many applications. Terrestrial applications would include measuring toxic and hazardous chemicals in field and industrial environments. Space applications include chemical and isotopic analysis of materials on extraterrestrial bodies. Minimization of weight are important for both these applications.
FIG. 1 shows a double-focusing mass spectrometer incorporating an electrostatic sector. Other details of the miniaturization of such mass spectrometers are found in our co-pending application numbers 08/600,861 and 08/881,705. This device is in the so-called Mattauch-Herzon geometry. The system described in this application is ideally used with a microbore, micromachined column gas chromatograph in order to analyze organic mixtures.
The mass spectrometer part is shown in FIG. 1. MS 99 includes an ion source 100 producing ion beam 101 passing through the object slit 102. Ion beam 101 continues through electrostatic sector 104 and then through a magnetic sector 107 where it is spatially dispersed according to masses of the particles along the focal plane and measured by a detector array 106. The electrostatic sector acts as an energy analyzer of the ions in the ion beams 101. Much of this is described in our co-pending application.
The electrostatic sector for such a mass spectrometer requires high precision fabrication. Moreover, it is important to properly align the electrostatic sector with other components of the analyzer. The two rails shown as 110 and 112 of the electrostatic sector require tight tolerance. For example, a common tolerance dimension is 5 to 10 .mu.m of parallelism for both the Y and Z directions where the ion motion is defined as the X direction in FIG. 1.
A complex and high precision housing to accommodate these rails is hence required.
These significant requirements have increased the cost of fabrication of such an electrostatic sector. These also increase the weight and volume of the electrostatic sector drastically. Alignment of the electrostatic sector with the rest of the mass is different and time consuming. Such electrostatic sectors are typically not sufficiently robust for field and space applications.